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https://issues.apache.org/jira/browse/CASSANDRA-14865?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16802256#comment-16802256
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Pedro Gordo commented on CASSANDRA-14865:
-----------------------------------------
I found the issue back in November but forgot to update the ticket. The cluster
had 3 DCs (2 in Europe and 1 in China). However, the application never writes
directly to DC in China, only through replication from the European DCs. This
resulted in a 0mu in the 99th percentile for system_auth.roles. Which meant
that any test query on it through cqlsh, always resulted in a speculative retry
for the roles table. But since this was just a result of test queries in cqlsh,
and not the normal read/writes from the application, it's ok.
Basically, it's a non-issue. :)
> Cascading calls to read retries, system_auth, and read repairs
> --------------------------------------------------------------
>
> Key: CASSANDRA-14865
> URL: https://issues.apache.org/jira/browse/CASSANDRA-14865
> Project: Cassandra
> Issue Type: Bug
> Components: Feature/Authorization
> Reporter: Pedro Gordo
> Priority: Normal
> Fix For: 3.11.1
>
> Attachments: cn_dc.txt, nec_dc.txt, wec_dc.txt
>
>
> Roles validity and permission cache values are the default ones. Same thing
> for the read-repair chance.
> We have a cluster with 3 data centers. We have noticed that in 2 of the data
> centers (NEC and CN) we have multiple calls to speculative read retries
> (rapid read protection), roles (instead of using cached values within the
> same tracing session), and multiple read repair messages.
> We would expect calls to roles, within sequential read sessions, because the
> cache could be turned, but not so many calls within the same tracing session.
> Same thing for read-retries, and read repair messages. We are discarding
> blocking read repairs possibility because we consistently get the same
> results when doing the query several times.
> It feels like something is cascading calls to these mechanisms regardless of
> conditions that would prevent them from being called (cached roles values for
> instance).
> I have attached tracing files from the 3 data centers. Please let me know if
> more info is needed.
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